Jenna Miscavige Hill opens up about how she left the church of Scientology in her memoir “Beyond Belief: My Secret Life Inside Scientology and My Harrowing Escape.”

In the book, she reveals “strange and disturbing details” about how she grew up in the church and provides her first-hand account of its upper ranks, according to the Associated Press.

Miscavige Hill, whose uncle is Scientology leader David Miscavige, has frequently criticized the religion since she publically broke with it in 2005.

She told investigative journalist Philip Recchia in 2008, “if you flunked your uniform inspection, sometimes if you were late . . . you would be dumped with a five-gallon bucket of ice water.”

She also commented about the organization’s most famous member, Tom Cruise, and his split with wife Katie Holmes. “As a mother myself, I offer my support to Katie and wish for her all of the strength she will need to do what is best for her and her daughter.”

Miscavige Hill claims that the church cut off all contact with her parents, who had left Scientology in 2000 when she was 16-years-old. Letters were allegedly intercepted and she was allegedly not allowed to answer the telephone for over a year.

After leaving the church, Miscavige Hill, with Kendra Wiseman and Astra Woodcraft—both also raised in Scientology—founded the website exscientologykids.com, a support group for ex-Scientology members.

“My experience in growing up in Scientology is that it is both mentally and at times physically abusive,” she said in a statement on the website.

Her book will be published by HarperCollins Publishers imprint William Morrow and will be out in January.